This paper investigates fracture mechanics based design of the adhesively bonded Single Lap Joint (SLJ) made with curved Fibre Reinforced Plastic (FRP) composite adherends having pre-embedded adhesion failures and surface ply delaminations at either end of the lap portion. The propagation of pre-embedded through-the-width delaminations and adhesion failures in the SLJ under uniaxial tensile load has been characterized by computing the Strain Energy Release Rates (SERR) near the adhesion failure/delamination fronts. The Virtual Crack Closure Technique (VCCT) has been used for the computation of SERR. Three Dimensional (3-D) non-linear Finite Element (FE) analyses of the SLJ have been carried out for these defects existing either individually or simultaneously at different locations. The predominant modes of failure, the radial location from where these defects may start to grow have been identified. The propagations of adhesion failures have been studied at the interfaces of the adhesive and the adherends by pre-embedding them in the region of high-stress concentrations. Similarly, the propagations of the delaminations are investigated by pre-embedding them beneath the surface ply of both the adherends at the vicinities of the overlap ends. The vulnerabilities of these damage fronts are compared at different locations in the joint for the overall assessment of the structural integrity of the SLJ. The longitudinal shearing mode of adhesion failure is the dominant mode irrespective of their position. The adhesion failure in the lap adherend is more detrimental than the adhesion failure pre-embedded in a similar location at the interface of the strap adherend with the adhesive. The influence of the locations of delaminations when they grow in size on the structural integrity of the joint has also been analysed. The maximum values of SERRs and their radial locations in all the delamination fronts at several locations have been pointed out for structural design purposes. The dominating mode of failure in delamination fronts is highly sensitive to their locations. The growth rates are found to be significantly different in the lap and the strap adherends even for similar locations. It has been observed that the initially straight damage front will gradually tend to be curved in shape.

本文研究了基于断裂力学的单弯接头（SLJ）的设计，该接头是由弯曲的纤维增强塑料（FRP）复合被粘物制成的，该复合被粘物具有预先埋入的粘结故障，并且在搭接部分的任一端都有表面层离层。通过计算在粘合破坏/分层前沿附近的应变能释放速率（SERR），可以表征单轴拉伸载荷下SLJ中预埋的贯穿分层和粘合破坏的传播。虚拟裂纹闭合技术（VCCT）已用于SERR的计算。针对这些缺陷的SLJ进行了三维（3-D）非线性有限元（FE）分析，这些缺陷要么单独存在，要么同时存在于不同位置。失败的主要方式 已经确定了这些缺陷可能开始生长的径向位置。通过在高应力集中区域预嵌入粘合剂和被粘物的界面，研究了粘附失败的传播。类似地，通过在重叠端附近将预嵌入两个粘附体的表面层之下来研究分层的传播。比较这些损伤前沿的脆弱性，在关节的不同位置进行比较，以全面评估SLJ的结构完整性。粘附失效的纵向剪切模式是主导模式，而与它们的位置无关。与预埋在带状被粘物与粘合剂的界面的相似位置中的粘着故障相比，搭接被粘物中的粘着故障更有害。还分析了分层的位置在尺寸增大时对接缝结构完整性的影响。为了结构设计的目的，已经指出了在多个位置的所有分层前沿中的SERR的最大值及其径向位置。分层前沿的主要失效模式对它们的位置非常敏感。发现即使在相似的位置，膝部和表带粘附体的生长速度也有显着差异。已经观察到，最初笔直的破坏锋线将逐渐趋于弯曲。还分析了分层的位置在尺寸增大时对接缝结构完整性的影响。为了结构设计的目的，已经指出了在多个位置的所有分层前沿中的SERR的最大值及其径向位置。分层前沿的主要失效模式对它们的位置非常敏感。发现即使在相似的位置，膝部和表带粘附体的生长速度也有显着差异。已经观察到，最初笔直的破坏锋线将逐渐趋于弯曲。还分析了分层的位置在尺寸增大时对接缝结构完整性的影响。为了结构设计的目的，已经指出了在多个位置的所有分层前沿中的SERR的最大值及其径向位置。分层前沿的主要失效模式对它们的位置非常敏感。发现即使在相似的位置，膝部和表带粘附体的生长速度也有显着差异。已经观察到，最初笔直的破坏锋线将逐渐趋于弯曲。为了结构设计的目的，已经指出了在多个位置的所有分层前沿中的SERR的最大值及其径向位置。分层前沿的主要失效模式对它们的位置非常敏感。发现即使在相似的位置，膝部和表带粘附体的生长速度也有显着差异。已经观察到，最初笔直的破坏锋线将逐渐趋于弯曲。为了结构设计的目的，已经指出了在多个位置的所有分层前沿中的SERR的最大值及其径向位置。分层前沿的主要失效模式对它们的位置非常敏感。发现即使在相似的位置，膝部和表带粘附体的生长速度也有显着差异。已经观察到，最初笔直的破坏锋线将逐渐趋于弯曲。